A milking system is one of the most important components on a dairy farm. It is used more hours per year than any other type of equipment on the farm. A key component of a milking system is the vacuum pump which is used to remove air from the milking system pipelines to create a partial vacuum.
The vacuum levels normally used for milking range from 13 to 15 in-Hg. Conventional systems use an oversized vacuum pump for vacuum stability when a milking unit falls off. In such a case, air flow changes by 20 to 35 cfm.
In a conventional system, the milking vacuum level is maintained by a vacuum controller which regulates the desired vacuum level by admitting external air as necessary when the vacuum reaches the predetermined setting. In the conventional system, the vacuum controller is sized to admit full vacuum pump capacity at the system's operating vacuum level. Vacuum fluctuations caused by changes in air usage, teat cup attachment, liner slip and unit fall-off, are compensated by the vacuum controller. The sensitivity of the controller should be such that there will be not more than about.+-.0.5 in-Hg vacuum fluctuation in a properly sized and maintained milking system, as measured in the main vacuum supply line.
Considerable energy is wasted by the vacuum pump/motor on dairy farms. The output capacity (cfm) of the vacuum pump always exceeds the capacity needed to milk cows and wash pipelines. Vacuum pumps run at full speed and load regardless of actual need for air.
In the conventional system, the vacuum level is maintained at +/-0.5 in-Hg by admitting or restricting air flow through a controller/regulator system. This traditional method of maintaining a constant vacuum at varying air flows is energy inefficient.
There is a need to provide an improved vacuum milking system which operates more efficiently than the conventional fixed pump speed system.
It is, therefore, an object of the present invention to provide an improved vacuum milking system wherein the energy requirement for maintaining the required vacuum level is markedly reduced over conventional vacuum pump milking systems.
A further object of the invention is the provision of a two-level vacuum system and process wherein the low-side vacuum can be maintained at a selected level with a specified tolerance or variance by feedback adjustment of the speed of the high-side vacuum pump motor.
A further object of the invention is the provision of a dual-vacuum controller for monitoring the vacuum in the low-vacuum end (pipeline) of a system subject to occasional leakage and to stabilize the vacuum in that low-vacuum end during periods of vacuum disturbances by connecting the low-vacuum end to a high-vacuum reserve through a regulator.
Another object of the invention is to provide a method for maintaining with minimum variance the stability of a specified low vacuum.